com.opensymphony.xwork2.conversion.impl

Class InstantiatingNullHandler

java.lang.Object

com.opensymphony.xwork2.conversion.impl.InstantiatingNullHandler

All Implemented Interfaces:

NullHandler

public class InstantiatingNullHandler
extends Object
implements NullHandler

Provided that the key ReflectionContextState.CREATE_NULL_OBJECTS is in the action context with a value of true (this key is set only during the execution of the ParametersInterceptor), OGNL expressions that have caused a NullPointerException will be temporarily stopped for evaluation while the system automatically tries to solve the null references by automatically creating the object.

The following rules are used when handling null references:

• If the property is declared exactly as a Collection or List, then an ArrayList shall be returned and assigned to the null references.
• If the property is declared as a Map, then a HashMap will be returned and assigned to the null references.
• If the null property is a simple bean with a no-arg constructor, it will simply be created using the ObjectFactory.buildBean(java.lang.Class, java.util.Map) method.

For example, if a form element has a text field named person.name and the expression person evaluates to null, then this class will be invoked. Because the person expression evaluates to a Person class, a new Person is created and assigned to the null reference. Finally, the name is set on that object and the overall effect is that the system automatically created a Person object for you, set it by calling setUsers() and then finally called getUsers().setName() as you would typically expect.

Author:

Matt Ho, Patrick Lightbody

Constructor Summary

Constructors

Constructor and Description
InstantiatingNullHandler()

Method Summary

Modifier and Type	Method and Description
Object	nullMethodResult(Map<String,Object> context, Object target, String methodName, Object[] args) Method called on target returned null.
Object	nullPropertyValue(Map<String,Object> context, Object target, Object property) Property in target evaluated to null.
void	setObjectFactory(ObjectFactory fac)
void	setObjectTypeDeterminer(ObjectTypeDeterminer det)
void	setReflectionProvider(ReflectionProvider prov)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

InstantiatingNullHandler

public InstantiatingNullHandler()

Method Detail

setObjectTypeDeterminer

public void setObjectTypeDeterminer(ObjectTypeDeterminer det)

setReflectionProvider

public void setReflectionProvider(ReflectionProvider prov)

setObjectFactory

public void setObjectFactory(ObjectFactory fac)

nullMethodResult

public Object nullMethodResult(Map<String,Object> context,
                               Object target,
                               String methodName,
                               Object[] args)

Description copied from interface: NullHandler

Method called on target returned null.

Specified by:

nullMethodResult in interface NullHandler

Parameters:

context - context

target - target object

methodName - method name

args - arguments

Returns:

object

nullPropertyValue

public Object nullPropertyValue(Map<String,Object> context,
                                Object target,
                                Object property)

Description copied from interface: NullHandler

Property in target evaluated to null. Property can be a constant String property name or a DynamicSubscript.

Specified by:

nullPropertyValue in interface NullHandler

Parameters:

context - context

target - target object

property - property

Returns:

object